The present invention relates to methods and devices for the testing of blood constituents, and more particularly to a blood test strip, and a method of using a blood test strip to prepare a blood sample for analysis.
In recent years, there has been a marked increase in the awareness of health issues. One manifestation of this awareness is that an increased importance is being placed on the use of preventive medicine to maintain good health. The widespread adoption of preventative medicine has resulted in an increase in the frequency of the testing for certain conditions, such as abnormal glucose and cholesterol levels, which indicate the existence of a disease, or the propensity to acquire a disease or disorder.
The monitoring and detection of these conditions often is performed by analyzing a patient's blood to determine whether a particular substance exists in the patient's blood, or to determine the amount of that substance in a patient's blood. As a consequence of this increased monitoring, blood tests are being performed on a more frequent basis. Formerly, these tests were usually performed in large hospital or independent laboratories, for only large laboratories performed a sufficient volume of tests to justify the large expenditures often required for sophisticated laboratory equipment.
Recently, however, the trend in blood testing has been to utilize blood tests which can provide a reliable qualitative or quantitative blood analysis without the need to utilize a large, expensive blood analyzing device located in a distant laboratory. To this end, tests have been devised which are suited for use by physicians in their office, and even patients in their homes.
One difficulty encountered in the testing of blood is that it is generally necessary to separate the plasma or serum component of the blood from the cellular components of the blood such as the red and white blood cells, as the presence of these cellular components usually interferes with the test. This problem can be especially acute in photometric or colorimetric reactions wherein the results of the test are often expressed as a color (or particular shade of a color) formed by the reaction of a chemical reagent with a component of the plasma or serum sample. Generally, this separation of the from the cellular components is performed by centrifugation. Recently, however, blood test strips have been designed which can separate the plasma from the cells contained in a blood sample. Examples of such test strips are disclosed in Vogel et. al., U.S. Pat. No. 4,477,575.
However, known blood test strips are generally incapable of collecting a defined volume of plasma and removing that plasma for subjection to chemical analysis. Furthermore, known blood test strips generally require the user to place a precisely measured amount of blood on the test strip.
It is one object of the present invention to provide a simple, yet versatile and easy to use blood test strip for separating the plasma or serum component of a blood sample from the cellular components, and for collecting the plasma or serum so separated in a manner which will enable the sample to be subjected to analysis to detect the presence or the concentration of a particular substance in the blood.